• 전기학회논문지P
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• 제67권4호
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• pp.221-226
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• 2018

In this paper, the power transfer efficiency analysis based on the resonant repeater in a magnetic resonance wireless power transfer system is proposed. The efficiency of the magnetic resonance method was verified by comparing the general frequency with the resonance frequency. The resonance repeater was arranged to increase the efficiency and increase the transfer distance. When using resonant repeaters, the maximum efficiency increase is about 36.23[%] and the transfer distance was extended to more than 20[cm]. Through this study, confirmed the effect of using resonance repeaters in wireless power transfer system. As a result, it can be expected that the overall technology related to wireless power transfer system will be more valuable for energy-IT technology.

• 한국초전도ㆍ저온공학회논문지
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• 제17권1호
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• pp.36-39
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• 2015

Many studies are being conducted to implement wireless charging, for example, for cellular phones or electronic tooth brushes, via wireless power transmission technique. However, the magnetic induction method had a very short transmission distance. To solve this problem, the team of Professor Marin Soljacic proposed a magnetic resonance system that used two resonance coils with the same resonance frequency. It had an approximately 40% efficiency at a 2m distance. The system improved the low efficiency and short distance problems of the existing systems. So it could also widen the application range of wireless power transmission. Many studies on the subject are underway. In this paper, the superconductor coil was used to improve the efficiency of magnetic resonance wireless power transmission. The resonance wireless power transmission system had a source coil, a load coil, and resonance coils (a transmitter and a receiver). The efficiency and distance depended on the characteristics of the transmitter and receiver coils that had the same resonance frequency. Therefore, two resonance coils were fabricated by superconductors. The current density of the superconductor was higher than that of the normal conductor coil. Accordingly, it had a high quality-factor and improved efficiency.

• 한국해안·해양공학회논문집
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• 제36권4호
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• pp.138-148
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• 2024

다중공진 파력발전체는 파랑의 공진현상을 복합적으로 이용하여 실해역의 평상파 내습시에도 파랑을 증폭시켜 효율적인 발전이 가능하다. 공진에 의해 파랑이 증폭될수록 다중공진 파력발전체의 발전 효율이 증가하며, 발전 효율이 최대가 될 수 있도록 공진부의 형상 최적화가 필요하다. 다중공진 파력 발전체는 항만 공진부와 수로 공진부에서 파랑을 증폭시키며, 본 연구에서는 수로 공진부의 길이, 위치 등 다양한 조건에서 CFD 수치실험을 수행하여 조건 별 상관성을 분석하고 수로 공진부의 최적 형상을 도출하였다.

• Journal of Magnetics
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• 제20권1호
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• pp.57-61
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• 2015

In this paper wireless power transmission system based on magnetic resonance coupling circuit was carried out. With the research objectives based on the mutual coupling model, mathematical expressions of optimal coupling coefficients are examined. Equivalent circuit parameters are calculated by Maxwell software, and the equivalent circuit was solved by Matlab software. The power transfer efficiency of the system was derived by using the electrical parameters of the equivalent circuit. System efficiency was analyzed depending on the different air gap values for various characteristic impedances. Hence, magnetic resonance coupling involves creating a resonance and transferring the power without radiating electromagnetic waves. As the air gap between the coils increased the coupling between the coils were weakened. The impedance of circuit varied as the air gap changed, affecting the power transfer efficiency.

• 한국초전도ㆍ저온공학회논문지
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• 제20권1호
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• pp.23-27
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• 2018

As the wireless power transfer (WPT) technology based on strongly resonance coupled method realizes large power charging without any wires through the air, there are advantages compared with the wired counterparts, such as convenient, safety and fearless transmission of power. From this reason, the WPT systems have started to be applied to the wireless charging for various power applications such as train, underwater ship, electric vehicle. This study aims for the effect and characteristics of different inserted resonance coil between Tx and Rx coils for charging system of superconducting magnetic levitation (MAGLEV) train. The transfer efficiency and effect are evaluated with helix type, rectangular type copper resonance coil, and HTS resonance coil under bulb and HTS magnet load, respectively. The input power is adapted with radio frequency (RF) power of 370 kHz below 500 W.

• 전기학회논문지
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• 제63권6호
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• pp.776-779
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• 2014

In this paper, we analyzed the efficiency of magnetic resonance wireless power transmission (WPT) using superconductor coil according to the changing position of transmission and receiving coils. We implemented a WPT system using a magnetic resonance at a frequency of 63.1 kHz. Transmission and receiving coils using superconductor coil were wound on a spiral manner of diameter 100mm. For comparison, transmission and receiving coils using normal conductor coil were designed under the same condition. At a distance of 50mm, we measured efficiency when transmission-receiving coils were matched 25%, 50%, 75% and 100%. When a superconductor coil was applied to the transmission and receiving units, efficiency of WPT was very high. In addition, in the case of the superconducting transmission-receiving coils, when coils matched 100% the efficiency was 30% and matched 25% the efficiency was 8%.

• 전기학회논문지
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• 제62권6호
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• pp.762-766
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• 2013

Interest in Wireless Power Transmission (WPT) technology has been increasing worldwide recently. This trend is proved by commercialized products such as electric toothbrush, wireless razor, and wireless charger for mobile phone battery. Studies for enhancing the applicability of the technology have been continuously conducted. Currently the WPT technology is based on the technologies using microwave, inductively coupling, and magnetic resonance. In the meantime, development of the microwave-based WPT faces difficulty due to health hazards involved in the technology, and application of the WPT technology using inductively coupling is restricted by area due to the problem of transmission length. In comparison, the WPT technology using magnetic resonance draws attention in terms of efficiency and transmission length. In this study, the sending coil based on the WPT technology using magnetic resonance system was replaced with an HTS coil to enhance transmission efficiency. Since the HTS coil has a zero resistance, power transmission loss can be minimized. At the same time, size of the current density could be increased to 100 times or more than typical coils. In addition, through impedance matching of LC device, maximal resonance properties were induced and consequently, frequency selection quality characteristics or Q was enhanced. As a result, the WPT type using the HTS coil showed a longer transmission length and better transmission efficiency compared with the WPT type using typical coils.

• 조명전기설비학회논문지
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• 제26권1호
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• pp.75-81
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• 2012

In this paper, the wireless power transfer system using the magnetic resonance was designed, analyzed by circuit analysis methode and the calculated transfer function was compared with the measured one. The self-resonant coil was made up of the commonly used capacitor which had the lumped capacitance and it enabled the stable magnetic resonance not to be affected by the circumstance. The transmission efficiency of this system was 70[%] at the 15[cm] between the transmission and receiving coil and the measured transfer function was similar to the calculated one, which means the circuit analysis methode is valid in this system. When the intermediate coils were added between the transmission and receiving coil, the transmission efficiency was increased, which produced the increase of transfer distance. In the case of the five intermediate coils adding, the 35[%] transmission efficiency was achived at the 90[cm] distance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1613-1616
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• 2008

A Transcutaneous Energy Transmission System (TET) has been developed for the wireless energy transmission with two magnetically coupled coils. A resonance circuit is used to raise the induced voltage and current of the secondary coil. Its resonance frequency depends on the internal resistance of circuit and the transferred energy. Because the transferred energy usually changes in wide range, the output voltage is unstable and the energy transferring efficiency decrease. A push-pull class E amplifier is usedto generate high frequency AC voltage. To maintain proper resonance frequency, the voltage output of the amplifier was continuously monitored and adjusted to the optimized resonance frequency. Because of its high frequency (370 kHz), a phase lockedloop circuit and a comparator are used to monitor the output waveform. The results of experimentaldata show that the PLL circuit can increase the transmission efficiency and stabilize the output voltage of TET.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.46-49
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• 2016

The wireless power transfer (WPT) system using a magnetic resonance was based on magnetic resonance coupling of the transmission and the receiver coils. In these system, it is important to maintain a high quality-factor (Q-factor) to increase the transmission efficiency of WPT system. Our research team used a superconducting coil to increase the Q-factor of the magnetic resonance coil in WPT system. When the superconductor is applied in these system, we confirmed that transmission efficiency of WPT system was higher than normal conductor coil through a preceding study. The efficiency of the transmission and the receiver coil is affected by the magnetic shielding effect of materials around the coils. The magnetic shielding effect is dependent on the type, thickness, frequency, distance, shape of materials. Therefore, it is necessary to study the WPT system on the basis of these conditions. In this paper, the magnetic shield properties of the cooling system were analyzed using the High-Frequency Structure Simulation (HFSS, Ansys) program. We have used the shielding materials such as plastic, aluminum and iron, etc. As a result, when we applied the fiber reinforced polymer (FRP), the transmission efficiency of WPT was not affected because electromagnetic waves went through the FRP. On the other hand, in case of a iron and aluminum, transmission efficiency was decreased because of their electromagnetic shielding effect. Based on these results, the research to improve the transmission efficiency and reliability of WPT system is continuously necessary.